1. Field of the Invention
The present application claims priority on Japanese Patent Application No. 2009-156516, filed on Jul. 1, 2009, the contents of which are incorporated herein by reference.
The present invention relates to a hybrid operating machine, an engine of which is assisted with a motor generator.
2. Description of Related Art
In recent years, for power generation machines for construction machines and the like, performances, such as energy efficiency, low pollution, and low noise, which take the Earth's environment into consideration, have been in demand. In order to satisfy these requirements, operating machines, such as a hydraulic excavator, which utilize an electric motor instead of a hydraulic pump or as assistance of engines, such as an internal-combustion engine, have appeared. In an operating machine incorporating the electric motor, the surplus kinetic energy generated from the electric motor is converted into electrical energy, and is stored in a capacitor, etc.
When engine load increases, and number of revolutions decreases, the engine speed can be brought close to a target engine speed by operating a motor generator as the electric motor according to the deviation of a real engine speed from the target engine speed, thereby performing torque assistance (Japanese Unexamined Patent Application Publication No. 2005-210870).